1. Field of the Invention
This invention relates to an electromagnetic induction heating cooker for a kitchen or cookery, and more particularly an electromagnetic induction heating cooker for using compatibly with the power supply of 100 volts and 220 volts by simple switching operation.
2. Description of the Prior Art
The conventional electromagnetic induction cooker generally tends to make it difficult to employ a transformer which can vary the voltage of power supply, since it has a consuming electric power of approximately 1.2 kilowatts while being of a small bulk or size and of a very light weight.
For example, in the prior art electromagnetic induction heating cooker as shown in FIG. 1, when the AC power supply is applied by the power when switch S.sub.1 on, it is converted into DC fullwave pulsating current by a bridge diode 10. The plus or positive voltage of said pulsating current components converted in such manner is fed via the filter comprising a choke coil L and a capacitor C.sub.3 to a resonant capacitor C.sub.4 and a work coil 30 while the minus or negative voltage is coupled to both an emitter terminal of power transistor Q.sub.1 and an anode of diode D.sub.1. On the one hand, as the AC voltage is applied via a transformer T to the control circuit 40, a control signal is output from the control circuit 40 to swiftly perform the operation of turning on and off repeatedly, thereby directing a high-frequency current to a work coil 30.
Because a magnetic line of force is generated in an output coil 30 by such a high-frequency current, an induction current flows in the magnetic vessel or container 20 (what is commonly called an Eddy Current), which then is converted into heat by the skin resistance of the magnetic vessel 20 to heat the contents of the vessel.
However, such a prior art electromagnetic induction heating cooker has a drawback in that it can exclusively operate with a 100 volt AC power supply or a 220 volt AC power supply but it can not be compatibly used with an AC power supply of 100 volts and with an AC power supply of 220 volts.